German patent document DE 10 2005 056 522 A1 discusses a gas sensor, which operates according to the double chamber principle and has two electrochemical pump cells, each of which has an electrode disposed in a measuring chamber with whose aid gas molecules can be pumped between the measuring chamber and the environment. The first pump cell is connected to the gas stream in order to detect the particles to be detected in the gas stream. The second pump cell is connected as reference to a reference-gas stream, which in principle contains no particles to be detected. The electrodes of the pump cells each cooperate with an antipolar counter electrode assigned to them, so that it is possible to tap a measuring signal, in particular an electric current, at the individual electrodes. The ratio of the measuring signal received from the first electrode and the reference measuring signal received from a second electrode is a measure for the concentration of the particles to be detected, in particular NOx.
A disadvantage of such a gas sensor is that especially very low concentrations are unable to be detected because such measuring signals are lost in the signal noise. In particular, such measuring signals cannot be differentiated from possible interference resulting, for instance, from instabilities or electric incouplings. Furthermore, it is possible that the measuring signal changes due to aging manifestations of the gas sensor, this change of the measuring signal being unable to be considered in the concentration measurement.